Regulations on the emission of harmful substances included in an exhaust gas from a car have been more and more strict, and it is considered in the U.S. that a car-mounted diagnosis device of the emission will be essential in 2010.
Moreover, it is also reported that even a gasoline vehicle discharges a larger amount of particulates (a particulate matter (PM)) than a diesel vehicle on which a particulate collecting filter (DPF) is mounted, in a case where the gasoline vehicle has a system for directly jetting a fuel into a cylinder.
In Patent Document 1, it is noted that particulates included in the exhaust gas are made of particulates having conductivity, and there are disclosed a particulate detection device and a particulate detection filter utilizing a fact that the electric resistance of an electric insulating member decreases, when the conductive particulates are attached to or adsorbed by the member.
Moreover, in Patent Document 2, a technology is disclosed in which light emitted from a light source is transmitted through the flow of the exhaust gas and received by a light receiving portion, and the light impermeability of the exhaust gas having a constant correlation function between the gas and the concentration of the particulates is detected, whereby the impermeability is converted into the concentration of the particulates by control means.
Patent Document 1: JP-A-59-060018
Patent Document 2: JP-A-04-203413